Analog signal switches have been developed in a multitude of forms. The most popular employ a large area junction field effect transistor (JFET) as the switch. This JFET is designed to have a low on resistance compatible with the analog circuit being switched. The JFET gate is driven, to switch the device, by a circuit that must be capable of charging and discharging the gate (plus stray) capacitance as rapidly as required for the designed switching speed. This typically involves high-current, high-slew-rate amplifiers. Since the analog signals being switched often have d-c components associated, along with faily large signal levels, the JFET gate must track the analog signal in the on state to make sure that the switch stays on. The above requirements place severe demands upon the gate switching circuits. Many prior art circuits operate well for some but not all requirements. For example, many circuits operate well but draw excessive quiescent current in the on state, off state, or both.
Finally, the circuit should be capable, if desired, of not inducing transients into the analog circuits being switched. Some of the prior art circuits work well, but, when they slew the JFET gate, have a tendency to shock excite the circuits connected to the source-drain portion of the JFET switch.